<HTML><HEAD><TITLE>update(+Tree0, ++Key, ?Value, -Tree)</TITLE>
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<H1>update(+Tree0, ++Key, ?Value, -Tree)</H1>
Update the value corresponding to a key in a tree.
<DL>
<DT><EM>Tree0</EM></DT>
<DD>A 2-3-4 tree
</DD>
<DT><EM>Key</EM></DT>
<DD>A key to update
</DD>
<DT><EM>Value</EM></DT>
<DD>The value corresponding to Key
</DD>
<DT><EM>Tree</EM></DT>
<DD>The tree after updating
</DD>
</DL>
<H2>Description</H2>
	<P>
	If the key Key already exists in the tree Tree0, then this predicate
	updates the corresponding value to be Value.  The resulting tree is
	Tree.
	</P>
	<P>
	This predicate should only be called with trees created by other
	predicates from the tree234 module.
	</P>
	
<H3>Fail Conditions</H3>
Fails if Key does not appear in Tree0.
<H3>Resatisfiable</H3>
no
<H2>See Also</H2>
<A HREF="../../lib_public/m_tree234/insert-4.html">insert / 4</A>, <A HREF="../../lib_public/m_tree234/set-4.html">set / 4</A>
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